Physico-mechanical characteristics and durability of calcium aluminate blended cement subject to different aggressive media

• Published in: Construction & building materials Vol. 78; pp. 379 - 385
• Main Authors: Heikal, Mohamed, Radwan, M.M., Al-Duaij, O.K.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.03.2015; Elsevier B.V
• Subjects: Air-cooled slag; Analysis; Building materials; Cement; Durability; Mechanical properties; Service life; Water-cooled slag and calcium aluminate cement; United States; Durability; Air-cooled slag; Water-cooled slag and calcium aluminate cement
• ISSN: 0950-0618
• DOI: 10.1016/j.conbuildmat.2015.01.033

•Compressive strength of CAC pastes is lower than CAC–WCS and CAC–ACS pastes.•20 mass% of CAC–WCS or CAC–ACS improve the physico-mechanical properties of CAC-blended pastes.•Compressive strength of CAC–WCS pastes are higher than those of CAC–ACS pastes.•Compressive strength of CAC in aggressive solution increases at 90days, then decrease up to 120days.•The thin flaky-plate like of C2ASH8 reflects the closed and compact texture in aggressive solutions. Three mixes were prepared from calcium aluminate cement (CAC) and 20 mass% water-cooled (WCS) slag or air-cooled slag (ACS). The pastes were prepared with the required water of standard consistency, cured under tap water until time of testing (1, 3, 7 and 28days). The durability of calcium aluminate blended cement was investigated by immersing the samples under tap water for 7days (zero time), and then immersed in 5% sodium chloride, 5% magnesium sulphate and 5% ammonium sulphate as aggressive media. Compressive strength, bulk density and apparent porosity were measured. X-ray diffraction analysis and scanning electron microscopy were studied to reveal their mineralogical and microstructural features. Compressive strength of neat CAC pastes are lower than those of CAC–WCS and CAC–ACS blends. Compressive strength of CAC pastes immersed in 5% NaCl, 5% MgSO4 or 5% (NH4)2SO4 increases with curing time up to 90days and then shows a slightly decrease up to 120days immersion time. The presence of Cl− or SO42− ions activates the hydration rate of CAC, CAC–WCS and CAC–ACS. The SEM micrographs of CAC–WCS and CAC–WCS indicate the presence of the thin flaky-plate like morphology of C2ASH8 and thin fibrous particles of C–S–H I,II, which reflects closed and compact texture.